US embassy spokesman Richard Buangan urged the authorities to lift the restrictions on Mr. Liu’s wife Liu Xia, saying “her rights should be respected and she should be allowed to move freely without harassment.”

That follows President Obama’s call for the release of Liu, who is currently serving an 11-year sentence for “incitement to subversion” because of his role in authoring a pro-democracy petition.

Such calls have irked a Beijing already on the defensive over the award.

Chinese Foreign Ministry spokesman Ma Zhaoxu Tuesday attacked “politicians in some countries” who he said had shown “disrespect for China’s judicial system” that “puts a big question mark on their true intentions.”

Official Chinese media have expressed shock that a man the authorities have branded a criminal should be awarded the globally respected Nobel prize.

“We oppose anyone using this matter to stir up a fuss and oppose anyone interfering in China’s internal affairs,” said Mr. Ma said at a regular press briefing Tuesday, when asked to comment on Mr. Obama’s declaration of support for Liu.

Mrs. Liu has been in police custody since just after the prize was announced on Friday evening. She was taken to see her husband in jail, and since her return to Beijing has been told she may not leave her apartment except under police escort, according to Liu’s lawyer Shang Baojun, who has spoken to her by phone.

Policemen are guarding the entrance to the residential compound where Liu Xia lives, and have disabled the mobile phone that she was using. A brother brought her a new one, according to friends, allowing her to communicate occasionally by Twitter, though she has generally remained silent except to re-Tweet messages of support she has received.

On Monday, a delegation of European diplomats was barred by police from visiting Ms. Xia. They had intended to deliver a letter of congratulations from the head of the European Commission Jose Manuel Barroso.

Ma did not respond to a journalist who asked why Ms. Liu should be under house arrest since she has not been charged with any offense. The Chinese authorities often use what is known here as “soft detention” to keep foreign journalists and other visitors away from politically sensitive figures, in order to muffle their voices.